ul,ol{
    list-style: none;
    padding-inline-start: 0;
}

a{
    color: black;
}

a:hover{
    text-decoration: none;
}

#course>ul>li{
    padding: 10px 0;
}


small{
    color: #6dd8ff;
}

/*!* 右半部分  *!*/

/*.video_click{*/
/*    position: relative;*/
/*}*/


/*!*.container-fluid .row>div:hover{*!*/
/*!*    padding: 0 10px;*!*/
/*!*}*!*/

/*.video_time{*/
/*    position: absolute;*/
/*    bottom: 0;*/
/*    right: 0;*/
/*    height: 21px;*/
/*    line-height: 21px;*/
/*    color: #FFFFFF;*/
/*    font-size: 14px;*/
/*    padding: 0 6px;*/
/*    border-radius:0.3em;*/
/*    background: rgba(38, 38, 54, 0.9);*/

/*}*/


/*图片遮罩层*/
.box{
    text-align: center;
    overflow: hidden;
    position: relative;
}
.box:before{
    content: "";
    width: 0;
    height: 100%;
    background: #000;
    padding: 14px 18px;
    position: absolute;
    top: 0;
    left: 50%;
    opacity: 0;
    transition: all 200ms cubic-bezier(0.47, 0, 0.745, 0.715) 0s;
}
.box:hover:before{
    width: 100%;
    left: 0;
    opacity: 0.5;
}
.box img{
    width: 100%;
    height: 10vw;
}
.box .box-content{
    width: 100%;
    color: #fff;
    position: absolute;
    top: 38%;
    left: 0;
}
.box .title{
    line-height: 30px;
    text-transform: uppercase;
    margin: 0;
    opacity: 0;
    transition: all 0.5s ease 0s;
}

.box:hover .title{
    opacity: 1;
    transition-delay: 0.2s;
}

@media only screen and (max-width:990px){
    .box{ margin-bottom: 30px; }
    .box img{
        width: 100%;
        height: 20vw;
    }
}

/**给左半部分的a标签添加样式**/
#course li:hover{
    background-color: WhiteSmoke;
}

.active{
    background-color: ghostwhite;
}